CVE-2014-5461 in Lua
Summary
by MITRE
Buffer overflow in the vararg functions in ldo.c in Lua 5.1 through 5.2.x before 5.2.3 allows context-dependent attackers to cause a denial of service (crash) via a small number of arguments to a function with a large number of fixed arguments.
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Analysis
by VulDB Data Team • 03/28/2022
The vulnerability identified as CVE-2014-5461 represents a critical buffer overflow condition within the Lua scripting engine that affects versions 5.1 through 5.2.x prior to 5.2.3. This flaw resides in the ldo.c source file and specifically impacts the vararg function handling mechanisms that Lua employs for managing variable argument lists. The buffer overflow occurs when the interpreter processes function calls that contain a small number of arguments but are defined with a large number of fixed parameters, creating a scenario where memory boundaries are exceeded during argument processing.
The technical implementation of this vulnerability stems from inadequate bounds checking within Lua's internal function call handling routines. When Lua encounters a function call with mismatched argument counts, particularly in scenarios where the function signature defines numerous fixed parameters while the actual call provides only a few arguments, the interpreter's argument processing code fails to properly validate memory allocation for the argument stack. This deficiency allows attackers to manipulate the argument processing flow through carefully crafted function calls that trigger memory corruption in the interpreter's internal buffers.
The operational impact of this vulnerability manifests as a denial of service condition that can cause the Lua interpreter to crash and terminate unexpectedly. Attackers can exploit this weakness by constructing malicious function calls that specifically target the vulnerable buffer handling code path, leading to unpredictable program termination and service disruption. The vulnerability is context-dependent meaning that successful exploitation requires specific conditions related to the function call patterns and argument structures being processed by the Lua interpreter. This makes the attack surface somewhat limited but still significant for applications that rely heavily on dynamic function calls or scripting capabilities.
From a cybersecurity perspective, this vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and represents a classic example of improper input validation in scripting environments. The attack pattern follows principles consistent with the ATT&CK framework's execution techniques, particularly those involving code injection and process manipulation through interpreter vulnerabilities. Organizations utilizing Lua-based applications should prioritize patching to version 5.2.3 or later, as this release includes the necessary fixes to properly validate argument counts and prevent the buffer overflow condition. The mitigation strategy should also include input validation controls at the application level to prevent malformed function calls from reaching the Lua interpreter, while monitoring for unusual patterns of function invocation that might indicate exploitation attempts.